Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. On top of that the description adds genuinely non-obvious context: the per-call cost of $0.05, the API key requirement, and the three-item cap, which matter to an agent deciding whether to call it.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

One sentence plus a short parenthetical; the resource and its cap are front-loaded, the default follows, and the cost/auth note is compactly bracketed. Nothing is redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple read-only single-parameter tool with an output schema (so return values need no explanation), the description covers scope, default, timezone, cap, cost and auth. Only the relationship to save_focus is left implicit.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema fully documents the single 'date' parameter as YYYY-MM-DD, and the description adds meaning beyond it by specifying the default (today) and the timezone basis (account timezone), which the schema does not state. Minor gap: no format or range details beyond that.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific resource (the user's daily focus items) with a scope limit (up to three) and a date selector, which is concrete enough to distinguish from the write counterpart save_focus. It does not explicitly name or contrast with any sibling, so it stops short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description supplies a useful default ('default today in the account timezone') that tells the agent it can omit the date, but it gives no explicit when-to-use guidance, no mention of save_focus for setting focus items, and no exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.